How do I place errorbars on my grouped bar graph using function ERRORBAR in MATLAB?

I use the following to create a grouped bar graph:

model_series = [10 40 50 60; 20 50 60 70; 30 60 80 90];
model_error = [1 4 8 6; 2 5 9 12; 3 6 10 13];
bar(model_series, 'grouped');
hold on
errorbar( model_series,model_error)

The result is a grouped bar graph with error bars placed in between each group of bars:

I would like to have "errorbar" place error bars on the center of each bar.

Answer 1

[MathWorks Support Team]

The ability to specify that the "errorbar" function should display the error bars inside the patches is not available in MATLAB.

There are two work arounds for this limitation, usage of which depends on the release of MATLAB that you are using.

For R2019a or earlier releases:

Find the center of each bar and pass this data into "errorbar" with the respective error values.

% Example data 
model_series = [10 40 50 60; 20 50 60 70; 30 60 80 90];
model_error = [1 4 8 6; 2 5 9 12; 3 6 10 13];
b = bar(model_series, 'grouped');

hold on
% Find the number of groups and the number of bars in each group
[ngroups, nbars] = size(model_series);

% Calculate the width for each bar group
groupwidth = min(0.8, nbars/(nbars + 1.5));

% Set the position of each error bar in the centre of the main bar
% Based on barweb.m by Bolu Ajiboye from MATLAB File Exchange
for i = 1:nbars
    % Calculate center of each bar
    x = (1:ngroups) - groupwidth/2 + (2*i-1) * groupwidth / (2*nbars);
    errorbar(x, model_series(:,i), model_error(:,i), 'k', 'linestyle', 'none');
end
hold off

For R2019b or later releases:

Retrieve the x coordinate of each bar using the "XEndPoints" property and pass this data into "errorbar":

https://www.mathworks.com/help/releases/R2019b/matlab/ref/matlab.graphics.chart.primitive.bar-properties.html#mw_3d0c5b61-b082-4c79-b9c6-a21152ae26ff

% Example data 
model_series = [10 40 50 60; 20 50 60 70; 30 60 80 90]; 
model_error = [1 4 8 6; 2 5 9 12; 3 6 10 13]; 
b = bar(model_series, 'grouped');

hold on
% Calculate the number of groups and number of bars in each group
[ngroups,nbars] = size(model_series);

% Get the x coordinate of the bars
x = nan(nbars, ngroups);
for i = 1:nbars
    x(i,:) = b(i).XEndPoints;
end

% Plot the errorbars
errorbar(x',model_series,model_error,'k','linestyle','none');
hold off

 

[KV]

This code works great - been able to test it for different types of bargraphs. However, it will be fantastic to understand how or why the following lines of code work:

groupwidth = min(0.8, numbars/(numbars+1.5));

and

x = (1:numgroups) - groupwidth/2 + (2*i-1) * groupwidth / (2*numbars);

Thank you!

[Oleg Komarov]

TK1234 answered with "You are brilliant". I moved his answer to the comment section here.

[Brian Muldoon]

This works very well. Thank you very much.

[Vera Elizabeth Thornton]

This generated a great looking bar plot! Thank you for sharing.

[LI]

Thank you! The code works great!

[Alessandro Leparulo]

Thank you! This code works well also for me! But, if i want to plot with this code only upper or lower error?

[Miraflor Santos]

It worked except that the error bars are to the side and not to the center of each bar. How would I correct this?

[Michael Abboud]

Hi Miraflor, this answer has been recently updated.

If the above method still results in uncentered error bars, I would suggest you look primarily at the 3rd-to-last line where the locations are calculated, or contact MathWorks Technical Support for further assistance.

[Jonathan Duncan]

it keeps say x to left is invalid assignment

[Mike]

Just required brackets, should work now if you replace with this line instead of what is there

x = (1:ngroups) - (groupwidth/2) + (2*i-1) * (groupwidth / (2*nbars));

[sdm sdm]

Could someone explain why the groupwidth is calculated with this?

groupwidth = min(0.8, numbars/(numbars+1.5));

[Erica Kiderman]

The groupwidth equation comes from the fact that the bar width property is specified as a fraction of the total space available for each bar and is 0.8 by default. In our case, the width of each individual bar (widthperbar) is 1 and the space between bar groups is 1.5 so to get the proper fraction -> numbars*widthperbar/(numbars*widthperbar+1.5) in this case since the width per bar is 1, that comes out to numbars/(numbars+1.5).

It also appears the code had a hidden invalid text character, which should explain the error. Thank you for bringing this to our attention. I have edited the answer above and there should no longer be an invalid character and should function as posted.

[Abby Lo]

I tried to run it in MATLAB R2017b but the error bars didn't show up. It showed the following error

Error (line 35) errorbar(x, model_series(:,i), model_error(:,i), 'k', 'linestyle', 'none');

[Jonathan Eicher]

Whenever I try to implement the second part of the script all the error bars revert to the center of the groups. If I plot the error bars by themselves tehy are all placed correctly spatially, but as soon as I try to apply it to the graph with my bars it all clusters towards the center of each group.

Any advice?

[Julia Hoskins]

I'm currently having the same issue as Jonathan Eicher with the 2019b and after script, so if anyone does have any advice for that it would be extremely beneficial.

[sankar basu]

No appropriate method, property, or field 'XEndPoints' for class

'matlab.graphics.chart.primitive.Bar'.

Error in grhist_errorbar (line 32)

x = [x ; b(i).XEndPoints];

[W. J.]

The example code is pretty badly written, not really Matlab style.

% Find the number of groups and the number of bars in each group
ngroups = size(model_series, 1);
nbars = size(model_series, 2);

can be written as

[ngroups, nbars] = size(model_series);

A for loop without preallocating properly the variables is also bad style:

% Get the x coordinate of the bars
x = [];
for i = 1:nbars
    x = [x ; b(i).XEndPoints]; % x changes size on every loop iteration!
end

The 2019b and later example should read:

%%For MATLAB 2019b or later releases
hold on;

% Calculate the number of groups and bars
[ngroups, nbars] = size(model_series);

% Get the x coordinate of the bars
x = nan(nbars, ngroups);
for i = 1:nbars
    x(i,:) = b(i).XEndPoints;
end
% Plot the errorbars
errorbar(x',model_series,model_error,'k','linestyle','none');
hold off;

The errorbar command should be terminated with a semicolon instead of an apostrophe!

[Thiviya Navaneethan]

Thank you for the feedback. We have updated the answer according to your suggestions.

[Markel Meseguer]

Hi

The solution works well for the example. However, when you add a categorical to the bar (X axe), the code does not work. I attach the codes:

R = rand(6,3,3);
error = R*0.1;
figure
barra = bar(R(:,:,1),'grouped');
hold on
for u = 1:3
    x(u,:) = barra(u).XEndPoints;
end
e1 = errorbar(x',R(:,:,1),error,'linestyle','none');

But if you add the categorical...

R = rand(6,3,3);
error = R*0.1;
X = categorical({'8 m/s +','8 m/s -','10 m/s +','10 m/s -','12 m/s +','12 m/s -'});
figure()
barra = bar(X,R(:,:,1),'grouped');
hold on
for u = 1:3
    x(u,:) = barra(u).XEndPoints;
end
e1 = errorbar(x',R(:,:,1),error,'linestyle','none');

Any idea on how to solve this problem? Thanks.

[Kjeld Kaj Klompmaker]

I have the same problem Markel, did you find a solution?

[Julia Marcinkowska]

I have exactly the same problem

My grouped bar chart is in three groups, and the error bars all appear in the centre of each bar group. I have used the code above for finding the dimensions of bars.

[ZenithWoman]

Try this

Y = [0.00083045,0.00092545,0.00090585;0.000864475,0.000883675,...
    0.00091715;0.0008724,0.000900175,0.00094375;0.00092295,0.000937475,...
    0.000954925;0.0010085,0.00103575,0.00111325;0.0012755,0.001303,0;...
    0.001835,0.0018805,0];%Y data
Y_er = [2.65534E-06,3.43093E-05,1.63905E-05;2.87529E-06,2.50012E-06...
    1.15358E-05;2.7377E-06,2.45064E-06,1.08844E-05;7.01029E-06,1.879E-06,...
    2.48475E-06;2.53311E-06,2.49583E-06,3.06526E-06; 3.32916E-06,...
    1.77951E-06,0;4.50925E-06,4.05175E-06,0];%The standard error of the means
cat_label = categorical({'Water';'#20-2.5';'#20-5';'#20-10'; '#20-20';'#20-50';'#20-100'}); %The Group Label
cat_label = reordercats(cat_label,{'Water';'#20-2.5';'#20-5';'#20-10'; '#20-20';'#20-50';'#20-100'});%To Preserve Label Order
b = bar(Y,'grouped');
hold on
% Calculate the number of groups and number of bars in each group
[ngroups,nbars] = size(Y);
% Get the x coordinate of the bars
x = nan(nbars, ngroups);
for i = 1:nbars
    x(i,:) = b(i).XEndPoints;
end
errorbar(x',Y,Y_er,'k','linestyle','none');%Adding the errorbars
hold off
set(gca,'xticklabel',cat_label)%This line should replace the numbers with your categorical label

Good luck!

Answer 2

[Iron1759]

I'm almost there..

I created a dynamic bar chart that compares different sets of data, it works partially (i.e. at XEndPoints).

How do I use another locations matix to adjust the YEndPoints as well?

[Maud Hendriksen]

How did you label the x-axis?

[Iron1759]

Hi,

If I understood your question, I used cell array in a for loop in the following way:

X{k} = convertStringsToChars(Sample_type{k});